This invention relates in general to facilitating driving of threaded screws, and more particularly to a device which enables a screw driver to be accurately associated with a threaded screw during driving of the screw without slippage.
Threaded screws are one of the most common forms of hardware used to fasten members together. Typically, a threaded screw has a slotted head which is engaged by a blade-like drive head of a screw driver. Rotation of the screw driver, either manually or by a power source, rotates the screw which then self feeds into the members to be joined, or into a complimentary threaded member. Universal problems associated with the driving of threaded screws are intitial alignment of the drive head with the screw slot and the slippage of the head from the slot during the driving action. In each instance, slippage of the blade-like drive head from the screw can cause damage to the surface (e.g., wood or aluminum) of the members being joined, or injury to the person using the screw driver.
In order to reduce the potential of slippage of the screw driver drive head from the screw, a class of screws referred to as Phillips head screws have been developed. The Phillips head screw has a cross-like slot engageable by a complimentary shaped drive head. While the occurance of slippage of the drive head from the slot in the screw is less likely than with the blade-like configuration, it has only been somewhat reduced. This is in part due to the fact that relatively more force is required at drive contact; therefore, relative rotational forces can still cause the drive head to slip out of the cross-like slot. Additionally, this slippage problem has been addressed by mechanical devices which clamp on to the screw driver and hold the the threaded screw relative to the driver head. Examples of such device are shown in U.S. Pats. No. 768,441 (issued Aug. 23, 1904 in the name of Fisher) and 2,723,694 (issued Nov. 15, 1955 in the name of Ross). However such devices are limited as to the geometry of the screw driver head that they can accomodate. Moreover, the manner in which they seat on the screw driver shaft allows for relative transverse movement of the devices relative to the associated screw driver heads. This results in difficulty in aligning the head with the screw.